Wafer defect inspection by neural analysis of region features

Wafer defect inspection is an important process that is performed before die packaging. Conventional wafer inspections are usually performed using human visual judgment. A large number of people visually inspect wafers and hand-mark the defective regions. This requires considerable personnel resources and misjudgment may be introduced due to human fatigue. In order to overcome these shortcomings, this study develops an automatic inspection system that can recognize defective LED dies. An artificial neural network is adopted in the inspection. Actual data obtained from a semiconductor manufacturing company in Taiwan were used in the experiments. The results show that the proposed approach successfully identified the defective dies on LED wafers. Personnel costs and misjudgment due to human fatigue can be reduced using the proposed approach.     

Easy preparation of crosslinked polymer films from polyoxyalkylene diamine and poly(styrene–maleic anhydride) for electrostatic dissipation

The curing reaction of polyoxyalkylene diamine and poly(styrene–maleic anhydride) was able to produce polymer films that were hygroscopic in nature. The process involved the formation of an imine intermediate by dissolving the diamine monomers in a ketone solvent, followed by instant casting into films before the solution self‐cured into a gel product. Hydrophilic films were formed by the fast reaction of amine with anhydride while evaporating the solvent under vacuum. The resulting films exhibited dissipation of electrostatic charges over a wide range, from 10^9.4 to 10^4.1 Ω/sq surface resistivity. The low resistivity was attributed to the functionality of hydrophilic polyoxyethylene (POE), which was able to adsorb moisture and optionally to the added metal ion salts. Furthermore, the slightly crosslinked network prevented POE from having crystallinity and rendered the films solvent resistant, thermally stable, and suitable for applications as antistatic and polymeric electrolytes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 716–723, 2007     

Application of Al/PI composite bumps to COG bonding process

This work demonstrates the probing, testability and applicability of Al/PI (aluminum/polyimide) composite bumps to the chip on-glass (COG) bonding process for liquid crystal display (LCD) driver chip packaging. The experimental results showed that the thickness of Al overlayer on PI core of the bump, the location of pin contact, and the bump configuration affect bump probing testability. The bump with type IV configuration prepared in this work exhibited excellent probing testability when its Al overlayer thickness exceeded 0.8 μm. We further employed Taguchi method to identify the optimum COG bonding parameters for the Al/PI composite bump. The four bonding parameters, bonding temperature, bonding time, bonding pressure and thickness of Al overlayer are identified as 180° C, 10 s, 800 kgf/cm² and 1.4 μm, respectively. The optimum bonding condition was applied to subsequent COG bonding experiments on glass substrates containing Al pads or indium tin oxide (ITO) pads. From the results of resistance measurement along with a series of reliability tests, Al pad is found to be a good substrate bonding pad for Al/PI bump to COG process. Excellent contact quality was observed when the bumps had Al overlayer thickness over 1.1 μm. As to the COG specimens with substrate containing ITO pads, high joint resistance suggested that further contact quality refinement is necessary to realize their application to COG process     

Optimization of turning operations with multiple performance characteristics using the Taguchi method and Grey relational analysis

This study investigated the optimization of CNC turning operation parameters for SKD11 (JIS) using the Grey relational analysis method. Nine experimental runs based on an orthogonal array of Taguchi method were performed. The surface properties of roughness average and roughness maximum as well as the roundness were selected as the quality targets. An optimal parameter combination of the turning operation was obtained via Grey relational analysis. By analyzing the Grey relational grade matrix, the degree of influence for each controllable process factor onto individual quality targets can be found. The depth of cut was identified to be the most influence on the roughness average and the cutting speed is the most influential factor to the roughness maximum and the roundness. Additionally, the analysis of variance (ANOVA) is also applied to identify the most significant factor; the depth of cut is the most significant controlled factors for the turning operations according to the weighted sum grade of the roughness average, roughness maximum and roundness.     

Leakage mechanism in Cu damascene structure with methylsilane-dopedlow-K CVD oxide as intermetal dielectric

This letter investigates the leakage mechanism in the Cu damascene structure with methylsilane-doped low-k CVD organosilicate glass (OSG) as the intermetal dielectric (IMD). The leakage between Cu lines was found to be dominated by the Frenkel-Poole (F-P) emission in OSG for the structure using a 50-nm SiC etching stop layer (ESL). In the structure using a 50-nm SiN ESL, the leakage component through SiN also made a considerable contribution to the total leakage in addition to the bulk leakage from trapped electrons in OSG. An appropriate ESL of sufficient thickness is essential to reduce the leakage for application to a Cu damascene integration scheme     

Mechanisms and solutions to gate oxide degradation in flash memory by tunnel-oxide nitridation engineering

Increasing attention has been paid to the peripheral gate-oxide integrity degradation of Flash memory devices that is induced by the tunnel-oxide nitridation. In this letter, the mechanisms of tunnel-oxide nitridation-induced degradation are characterized. We report that both a local oxide thinning effect and nitrogen residue will impact the integrity of gate-oxide. Minimizing the local thinning effect with an in situ steam generation (ISSG) oxidation process and removing the nitrogen residues from the silicon wafer surface by either an additional sacrificial oxide process or over-dip are proven to be useful in recovering the gate-oxide integrity. An optimum approach with the tunnel-oxide nitridation is proposed in this work that results in comparable or even better gate-oxide property than other approaches that have no tunnel-oxide nitridation process.     

IPNs based on unsaturated polyester/epoxy: IV. Investigation on hydrogen bonding,compatability and interaction behavior

A series of interpenetrating polymer networks (IPNs) based on unsaturated polyester/epoxy have been developed. The compatibility and interaction behavior of these IPNs have been investigated by DMA, DSC, SEM, FTIR and solid‐state NMR spectroscopies. The glass transition temperatures of IPNs were decreased and their transitions became broader as the content of unsaturated polyester increased in IPNs, based on our DMA and DSC study. The results of FTIR indicate that hydrogen bonding is present between the unsaturated polyester and epoxy. Insufficient degree of hydrogen bonding brought about immiscibility between IPN components. The analysis of proton spin‐lattice relaxation time in the rotating frame of the IPNs was also utilized to investigate molecular interaction between unsaturated polyester and epoxy. From relaxation curves, phase separation was found for the IPN samples with unsaturated polyester content higher than 30 %. This corroborates the DMA and SEM study. Copyright © 2004 Society of Chemical Industry     

Influence of pressure dependence of the yield criterion on the strain-rate-intensity factor

The strain-rate-intensity factor is the coefficient of the principal singular term in an expansion of the equivalent strain rate in a series in the vicinity of maximum-friction surfaces. Its value controls the physical processes in a thin material layer near the frictional interfaces. The objective of the present paper is to study the effects of the pressure dependence of the yield criterion on the strain-rate-intensity factor. The results can be used to develop new methods for predicting the evolution of material properties in the vicinity of surfaces with high friction in metal-forming processes.